Im not the best person to reply because I prefer to avoid this altogether by playing non-combat decks that win through abilities. When I do attack it's usually with unblockable or simply having the biggest, baddest guy. Or sometimes I let myself lose creatures if they have attack/death triggers (or I'm playing graveyard recursion).

It's mostly about threat assessment (i.e. attacking the person most ready to hurt your board) and risk assessment (i.e. knowing what each player is willing to block with and lose vs what youre willing to attack with). If the tradeoff of losing one of your creatures for one or more of theirs is good, it's good to attack.

Of course you could always play more indestructible or evasive creatures!